Motor lubricating oil composition



United tes MOTOR LUBRICATIN G OIL COMPOSITION Stanley R. Newman, Robert Y. Heisler, and Kenneth L. Dille, Fishkill, and Norman Alpert, Poughkeepsie, N.Y., assignors to The Texas Company, New York, N.Y., a corporation of Delaware No Drawing. Application November 19, 1956 Serial No. 622,772

6 Claims. (Cl. 252-l.5)

' This invention relates to motor lubricants containing a novel class of additives which reduce or suppress deposit formation in combustion engines. More specifi- .cally, this invention discloses that superior lubricating oils, from the standpoint of removal of low temperature deposits, are obtained by the addition thereto of a minor amount of a polyglycol carbamate of a prescribed composition.

As automobile manufacturers annually raise the compression ratio of their engines in the race for higher horsepower, the problem of engine deposits resulting from the fuel becomes increasingly more severe. Engine deposits which find their origin in the fuel are primarily responsible for surface ignition phenomena such as preignition 'and octane requirement increase (0R1) which is the tendency of spark ignition engines in service to require higher octane fuels for proper performance. There are two avenues by which this problem can be attacked.

One approach is through the fuel and the other is through I the lubricating oil. In a coassigned copending application filed of even date, Serial No. 622,809, now Patent No. 2,842,433, it is disclosed that superior hydrocarbon fuels from the standpoint of engine deposits result from the incorporation of a polyglycol carbamate of a prescribed composition. The present invention involves the discovery thatthe addition of a polyglycol carbamate to a lubricating oil produces lubricants marked by the ability to maintain a clean engine even with dirty fuels under low temperature conditions of operation.

I Modern lubricating oils for internal combustion en- I gines usually contain a combination of additives which impart detergent and dispersant properties as well as I resistance to oxidation to lubricating oils. The detergent and dispersant properties are normally obtained by the addition of alkaline earth metal petroleum sulfonates,

alkaline earth metal salts of alkyl-substituted aromatic compounds or derivatives of these compounds. The most commonly used anti-oxidant and inhibitor is a divalent tion are particularly designed for control of deposits resulting at low temperature conditions of operation.

. The improved lubricating oils of this invention contain a polyglycol carbamate ester of the general formula:

wherein R is hydrogen, an alkyl, alkenyl, or alkynyl group having from 1 to 18 carbon atoms, R is an alkyl,

alkenyl, or alkynyl group having from 1 to 18 carbon atoms, and n ranges from 2 to 6, in an amount sufiicient atent 2,879,230 I Patented Mar. 24, 1059 to reduce deposit formation in the engine. The polyglycol carbamate ester is effective in the motor lubricant in concentrations as low as 0.25 volume percent but concentrations of 0.5 to 3.0 volume percent are normally employed. There is no critical upper limit of concentration, but economic considerations dictate that concentrations less than 5.0 volume percent of the polyglycol carbamate ester be present in the lubricating oil.

The present invention also includes the method .of operating an internal combustion engine which com prises utilizing a fuel containing a polyglycol carbamate ester of the following general formula:

wherein R is hydrogen or an alkyl, alkenyl or alkynyl radical having from 1 to 18 carbon atoms, R is an alkyl, alkenyl or alkynyl radical having from 1 to 18 carbon atoms and n ranges from 2 to 6, said compound being present in the fuel and engine lubricant in amounts sufiicient to suppress the formation of engine deposits.

The range in which the polyglycol carbamate maybe used in the fuel in the process of this invention is from 0.01 volume percent up to about 1 volume percent, preferably from about 0.04 to 0.3 volume percent. The addition range of polyglycol carbamate in the engine lubricant of the process of the invention'is from 0.25 to 5.0 volume percent and preferably from 0.5 to 3 volume percent in the oil.

Polyglycol carbamates of the present invention include for example: diethylene glycol bis (N,N-diallyl carbamate); diethylene glycol bis [N,N-di-(l-methylisopentyl) carbamate]; diethylene glycol bis (N-Z-ethylhexyl carbamate); diethylene glycol bis (N,N-dipropargyl carbamate); diethylene glycol bis (N-allyl carbamate); diethylene glycol bis (N-n-propyl carbamate); diethylene glycol bis (N,N-diisobutyl carbamate); triethylene glycol bis (N,N-diallyl carbamate); triethylene glycol bis (N,N- dioctadecyl carbamate); triethylene glycol bis [N- 1,1- dimethyl-Z-propynyl) carbamate]; tetraethylene glycol bis (N-2-ethylhexyl carbamate); tetraethylene glycol bis (N-allyl carbamate); pentaethylene glycol bis (N-propargyl carbamate); pentaethylene glycol bis (N-n-propyl carbonate) hexaethylene glycol bis (N,N-diallyl carbamate); hexaethylene glycol .bis (N-n-butyl carbamate); and hexaethylene glycol bis (N-Z-ethylhexyl carbamate).

The polyglycol carbamate esters which inhibit the deposit-forming tendencies of hydrocarbon fuels are readily formed by a series of reactions involving the formation of a polyglycol dichloroformate and thereafter reacting said dichloroformate with an aliphatic hydrocarbon amine. The reaction product is then separated from the unreacted substances by known purification steps. The preparation of the polyglycol dichloroformate type compound is disclosed in U.S. Patents 2,370,567 and 2,370,569.

The following examples are given to demonstrate the preparation of the esters of the invention.

EXAMPLE I Preparation of diethyleneglycol bis (N-allyl carbamate) separated and the oil layer waswashed with 10 percent hydrochloric acid and then washed again with a saturated salt solution several times until the washes were neutral.

The solution was then filtered, and the benzene and water were removed by distillation at atmospheric pressure.

. The residue, 1369 g., was crystallized to a waxy solid of low melting point. This solid was recrystallized from ether to yield 991 g. of white crystals having a melting point of 50 to 53 F. The theoretical analysis for diethylene glycol bis (N-allyl carbamate) shows the compound to have 53.0 percent carbon; 7.36percent hydrogen, and 10.0 percent nitrogen. The actual anlysis of the compound formed in accordance with this example showed it to have 52.7 percent carbon; 7.37 percent hydrogen; and 9.8 percent nitrogen. The yield of the purified compound was 62' percent of the theoretical yield.

EXAMPLE II Preparation of diethylene glycol bis(N-2-ethylhexyl carbamate) 193 ml. (2.4 moles) of pyridine and 354 ml. (2.2 moles) of 2-ethylhexylamine were placed in a liter, triple-necked flask equipped with a stirrer, condenser, thermometer, and addition funnel. This mixture was stirred and maintained below 50 F. while 231 g. (1 mole) of diethylene glycol dichloroformate were slowly added. The solution changed from yellow to green to brown and finally to dark red. After about 15 hours of stirring, 500 ml. of ether was added and the resulting mixture was washed 5 times, each time with 400 ml. of 10 percent hydrochloric acid followed by 4 washes with 300 ml. of saturated salt solution per wash. The neutral water insoluble layer was dried over anhydrous. calcium sulfate. The calcium sulfate was next removed by filtration and the ether removed by vacuum distillation. The crude product of 350 g. was dissolved in benzene and twice passed through synthetic magnesium silicate to give a light orange solution. The benzene was removed by vacuum distillation. The product had a calculated analysis of 63.4 percent carbon; 10.54 percent hydrogen; 6.74 percent nitrogen; and a molecular weight of 416. An actual analysis of the product showed 62.2 percent carbon; 10.4 percent hydrogen; 6.6 percent nitrogen; and a molecular weight of 402.

. EXAMPLE III Preparation of diethylene glycol bis(N-n-propyl carbamate) lowed by 3 washes with 1000 ml..of water. The crude product was further purified by a synthetic magnesium silicate percolation, and the benzene was evaporated to give approximately 700 g. ofthe crude product. The product was again dissolved in benzene and decolorized by passing through decolorizing charcoal and cooled to recover 330 g. of white crystals. A small sample was dried over P at 65 F. under 2 mm. pressure. The product had a theoretic 52.1 percent carbon, 8.7'percent hydrogen, 10.12 percent nitrogen, and amolecular weight of 276. The actual analysis of the compound showed it :gto have 51.8 percent carbon, 7.5 percent hydrogen, and

-- v9.9 .percent nitrogen.

4 EXAMPLE 1V Preparation of diethyleneiglycol bis (MN-diallyl carbamate) 970 g. of diallylamine, 500 ml. of benzene, and 880 ml. of pyridine were placed into a triple-neck flask equipped with a stirrer, condenser,thermometer, and addition funnel. The mixture was stirred and maintained below 50 F. while 1155 g. of diethylene glycol dichloroformate were slowly added. After stirring for about hours, the mixture was washed with a 10 percent hydrochloric acid solution and thereafter washed again with a saturated salt solution. The remaining benzene and water were removed by distillation. The crude product weighed 1580 g. Further purification was made by vacuum distillation. Analysis of the fraction boiling at 173 to 195 F. at 300 to 750 microns was made.v This product theoretically had 61.1 percent carbon; 7.95 per- ,cent hydrogen; and 7.95 percent nitrogen. Actualanalysis of this compound show it contained 60.6 percent carbon; 7.95 percent hydrogen; and 7.8 percent nitrogen.

The lubricating oil of this invention is efiective in maintaining deposits at a low level with the results that an engine lubricated therewith shows exceptionally clean cylinder head, combustion space, valves and ring belt area. The low deposit level in the engine minimizes surface ignition in all its manifestations, mainly preignition and knock. In addition, the low deposit level reduces the engines octane requirement increase. Deposits on surfaces contacted by the additive-containing lubricating oil, such as piston skirts and cylinder walls, are very markedly reduced.

The polyglycol carbamates of this invention areefiective in controlling deposit formation in lubricants employed in spark ignition engines, diesel motors and gas turbines. However, they are normally used in motor oils for spark ignition engines wherein fuel derived deposits formed during low temperature operation are a particularly vexing problem. Diesel lubricants containing these polyglycol carbamates are effective in eliminatingdeposits resulting from the use of the so-called economy" diesel fuels, e. g., fuels having a high sulfur content or containing cracked or residual stocks. The polygly'col carbamates are also useful as deposit-control additives in gas turbine lubricants which are generally ester base lubricants. They are also useful in aviation oilswhich lubricate reciprocating aviation engines. The scopeof the lubricating oils to which the polyglycol carbamates of the invention are added with the formation of superior lubricants from the standpoint of deposit-removal is broad and includes mineral oils, synthetic lubricating oils as solvent dewaxing to remove waxy components and improve the pour of the oil. Broadly speaking, mineral lubricating oils having an SUS viscosity at 100 F.-"between 50 and 1,000 may be used in the formulationof the improved lubricants of this invention but usually the viscosity range falls between 70 and 300 at 100 F.

The mineral lubricating oils to which the additives of this invention are added usually contain other additives designed to impart other desirable properties thereto. Forexample, V.I. improvers, such as theqpolymethacrylates, are normally included therein as are-materials t which act as detergents and dispersants for the removed combustion chamber deposits.

5 I The VJ. improver-normally used is a polymethacrylate of the general formula:

Ha OHa.( 7

- is a divalent metal alkyl dithiophosphate which results from the neutralization of a P S -alcohol reaction product with a divalent metal or divalent metal oxide. The mostwidely used inhibitors are barium andzinc alkyl dithiophosphates. I

The synthetic lubricating bases are usually of the ester or ether type. High molecular weight, high boiling liquid aliphatic dicarboxylic acid esters possess excellent viscosity-temperature relationships and lubricating properties and are finding ever increasing utilization in lube oils adapted for high and low temperature lubrication; esters of this type are used in the formulation of jet engine oils. Examples of this class of synthetic lubricating bases are the diesters of acids such as sebacic, adipic, azelaic, alkenylsuccinic, etc. Specific examples of these diesters are di-Z-ethylhexyl sebacate, di-Z-ethylhexyl azelate, di-Z-ethylhexyl adipate, di-n-amyl sebacate, di-2- ethylhexyl n-dodecyl succinate, di-2-ethoxyethyl sebacate, di-2'-methoxy-2-ethoxyethyl sebacate (the methyl Carbitol diester), di-2'-ethyl-2-n-butoxyethyl sebacate (the 2-ethylbutyl Cellosolve diester), di-Z-n-butoxyethyl azelate (the n-butyl Cellosolve diester) and di-2-n-butoxy- 2-ethoxyethyl-n-octyl succinate (the n-butyl Carbitol diester).

Polyester lubricants formed by a reaction of an aliphatic dicarboxylic acid of the type previously described, a glycol and a monofunctional aliphatic monohydroxy alcohol or an aliphatic monocarboxylic acid in specified mole ratios are also employed as the synthetic lubricating base in the compositions of this invention; polyesters of this type are described in US. 2,628,974. Polyesters formed by reaction of a mixture containing specified amounts of dipropylene glycol, sebacic acid and 2-ethylhexanol and of a mixture containing adipic acid, diethylene glycol and 2-ethylhexanoic acid illustrate this class of synthetic polyester lubricating bases.

Polyalkylene ethers as illustrated by polyglycols are also used as the lubricating base in the composition of this invention. Polyethylene glycol, polypropyleneglycol, polybutylene glycols and mixed polyethylene-polypropylene glycols are examples of this class of synthetic lubricating bases.

The sulfur analogs of the above-described diesters, polyesters and polyalkylene esters are also used in the formulation of the lubricating compositions of this invention. Dithioesters are exemplified by di-2-ethylhexyl thiosebacate and di-n-octyl thioadipate; polyethylene thioglycol is an example of the sulfur analogs of the polyalkylene glycols; sulfur analogs of polyesters are exemplified by the reaction product of adipic acid, thioglycol and Z-ethylhexyl mercaptan.

The action of the polyglycol carbamates of this invention in improving the deposit-removing properties of a lubricating oil was demonstrated by a modified Chevrolet deposits test-CRC FL-2-650. The laboratory engines were operated under the standard conditions of this test with the exception that crankcase oil temperatures were F. lower, the water jacket temperatures were 5 F.

- lower, and the crankcases of the test engines were ventilated. These modifications were in every casein the direction of making the test more severe and were intended to simulate low temperature conditions wherein deposit formation is most pronounced. After the termination of each run, the engine was disassembled and its parts evaluated by a merit system adapted from the CRC-L-4-1252 test. p This merit system involved visual examination of the engine parts in question and their rating according to deposits by comparison with standards which had assigned ratings. For example,'a. ratingof 10 on piston skirt designated a perfectly clean" piston while a rating of zero represented the worst condition. Similarly, a rating of on total engine deposits represented a perfectly clean engine, etc.

The fuel used in this test was a high quality regular grade gasoline comprising a mixture of thermal cracked stock, fluid catalytically cracked stock and straight run gasoline. This regular base fuel haclan 87.0 ASTM research octane rating, contained 2.90 ml. of TELper gallon, had an API gravityof 58.0 and a boiling range between 106 F. and 396 F.; the base fuel was negative in the copper corrosion test and had an oxidation stability in the ASTM test of 530 minutes minimum. The reference fuel also contained minor amounts of gasoline inhibitors, namely, N,N'-di-secondary butyl-p-phenylene diamine, lecithin, and N,N'-disalicylidene 1,2-diamino propane. I

The reference lubricating oil was a 20-20W heav duty oil meeting supplement I requirements. This reference oil contained a methacrylate V.I. improver and a balanced combination of additives which impart detergent, dispersant and anti-oxidant properties to the oil. The additive mixture comprised a barium petroleum sulfonate, and a zinc alkyl dithiophosphate in which the alkyl group is a methylcyclohexyl radical.

In the following table the results obtained in the modified Chevrolet deposits test with lubricating oils having the additives of the invention therein are shown. In these experiments the concentration of additive in the lubricant was determined at the conclusion of the run by analysis.

DE G=diethylene glycol.

It is evident from the results shown in the above table that the compounds of the invention are very eflective deposit suppressors.

The following table sets forth the results of the method of operating a combustion engine wherein the additive of the invention is carried to the combustion chamber in both the fuel and the engine lubricant. The base fuel and the base lubricant were those described as used in the above-described Chevrolet S-II test.

TABLE IL-CHEVROLET S-II TEST RESULTS Piston Total Skirt Engine Rating Rating Reference Fuel and Reference Oil 6.1 80. 1 Reference fuel and 0.05 vol. 51, DEG bls(N,N-

dlallyl carbamate) and Reference oil plus 1.0 vol. DEG bls(N,N-diallyl carbamate) 8. 0 88. 0

.The great-improvement inerig'ine cleanliness as demonstrated; by-- the result obtained in theabovedeposits test gproves thenierit" of the method ofoperating acombustion engine in accordancewith the, present invention.

;Obviously,, many modifications and variations of the invention, as hereinbefore set'forth, may be made with- -out departing from :the spirit andscope thereof, and therefore only'such limitations should'beimposed as are indicated in the appended claims.

"We claim:

1; A lubricating oilcontaining a minor amount of a polyglycol carbamate having the following general forgwherein R is selected from the group consisting'jof hydrogen, alkyl, alkenyl and alkynyl, radicals having from 1 .to 18 carbon atoms, R is selected from the group consisting of alkyl, alkenyl and. alkynyl radicalshaving, from 1 to 18 carbon atoms, and n ranges from 2 to 6,1 in an amount suflicient to reduce engine deposits.

. fluid is from 0.25 to 5.0 volume. percent.

5. A mineral lubricatingoil containing from 0.5 to 3.0 volume percent of diethylene glycol bis(N,N-diallyl carbamate).

6. A mineral lubricatingroil containing from 0,5 to 3.0 volume percent. of, diethylene glycol. bis(N-2-ethylhexy1 carbamate) References. Cited inthe file of this patent UNITED STATES PATENTS 2,161,615 1 Dietrich June 6, 1939 r 2,438,452 Pollock Mar. 23, 1948 2,528,399 Strain Oct. 31,, 1950 2,657,984 Brathwaite Nov. 3; 1953 OTHER REFERENCES Motor 'Oils' and Engine Lubrication,Georgi, Reinhold Pub. Corp. (-1950), pages 337-342. 

1. A LUBRICATING OIL CONTAINING A MINOR AMOUNT OF A POLYGLYCOL CARBAMATE HAVING THE FOLLOWING GENERAL FORMULA: 